The focusing on sports and every extra curricular activity along with an emphasis on education beyond HS is critical. Since the JWs really push that education is bad as well as the evil influence of other *worldly* children, your kids need to see that this position of the JWs is pure and total crap, baloney and hogwash. They push that extra curricular activites be stopped because of the time it takes away from Field Service and Jehovah. (gag) If your kids tell you they enjoy Field Service, they are totally lying. Ask they truthfully, when your wife is not around. I guarantee you they hate it.
I'm sure they don't like going to the meetings either and wish you would get your wife off their backs. Why not push your wife a little? You, as the man, are Head of the Household, according to the JWs. You can make all the decisions and she is supposed to go along with them. (They are sexist bastards, BTW) This is the only time I would ever say be a sexist bastard) In this case, it could save your family.
A Cult such as the JWs will do everything it can to isolate them and make them feel that anyone outside of the Organization is evil and bad. This simply is not true. We all know that (now). These outside influences will allow your children to see you, their own father, as not being evil and bad. This will also give them the open minds they will need to attend college and hopefully not get baptized and hopefully leave the Organization. Hopefully your wife will also someday.
Leaving a Cult is difficult, however, it can be done. The key is not letting your children get sucked in if you can stop it in any way.